Verifying a user of a computer system

1. A computer-implemented method for verifying a user of a computer system, comprising:

observing behavioral characteristics of the user's interactions with the computer system during a current session of computer system usage, the behavioral characteristics being based on command invocation behavioral characteristics;

identifying variations between the observed behavioral characteristics and a behavioral profile developed based on prior command invocation behavioral characteristics of the user; and

implementing a verification procedure for the user to complete to continue the current session, the verification procedure being based on the identified variations between the observed behavioral characteristics and the behavioral profile;

wherein identifying variations between the observed behavioral characteristics and the behavioral profile includes, calculating a measure of distance between the observed behavioral characteristics and the behavioral profile, and wherein implementing a verification procedure for the user to continue the current session includes, defining a verification procedure based on the calculated measure of distance which includes a verification challenge to the user, the verification challenge being based on the identified variations between the observed behavioral characteristics and the behavior profile.

2. The method of claim 1 , further comprising:

developing the behavioral profile by identifying typical command invocation behavioral characteristics of the user from historical computer system usage data.

3. The method of claim 1 , wherein calculating a measure of distance between the observed behavioral characteristics and the behavioral profile comprises:

Calculating a Damerau-Levenshtein distance between the observed behavioral characteristics and the behavioral profile.

4. The method of claim 1 , wherein in the step of implementing a verification procedure for the user to complete to continue the current session, the challenge verification procedure is further based on a risk level of the current session.

5. The method of claim 4 , further comprising:

determining a risk level of the current session based on one or more requested activities of the current session.

6. The method of claim 1 , wherein the command invocation behavioral characteristics are selected from a group consisting of:

an order of command invocations;

a set of selected command options;

an order of entered command options;

a grammatical structure of a command invocation;

a set of words selected for a command invocation;

an order of words of a command invocation;

use of a shortcut for a command invocation;

a speed of command invocation;

a chosen method for a command invocation; and

a user input device used for command invocation.

7. The method of claim 1 , further comprising:

modifying the behavioral profile based on the observed behavioral characteristics of the user's interactions with the computer system during the current session of computer system usage.

8. The method of claim 1 , further comprising:

determining if the user is verified based on completion of the verification procedure by the user; and

if it is determined the user is verified, modifying the behavioral profile based on the identified variations between the observed behavioral characteristics and the behavioral profile.

9. The method of claim 1 , wherein the verification procedure comprises:

providing the verification challenge to the user, the verification challenge being based on the identified variations between the observed behavioral characteristics and the behavioral profile; and

permitting the user to continue the current session based on the user's response to the verification challenge.

10. A computer program product for verifying a user of a computer system, the computer program product comprising a computer readable storage medium having program instructions embodied therewith, the program instructions executable by a processing unit to cause the processing unit to perform a method comprising:

observing behavioral characteristics of the user's interactions with the computer system during a current session of computer system usage, the behavioral characteristics being based on command invocation behavioral characteristics;

identifying variations between the observed behavioral characteristics and a behavioral profile developed based on prior command invocation behavioral characteristics of the user; and

implementing a verification procedure for the user to complete to continue the current session, the verification procedure being based on the identified variations between the observed behavioral characteristics and the behavioral profile;

wherein identifying variations between the observed behavioral characteristics and the behavioral profile includes, calculating a measure of distance between the observed behavioral characteristics and the behavioral profile, and wherein implementing a verification procedure for the user to continue the current session includes, defining a verification procedure based on the calculated measure of distance which includes a verification challenge to the user, the verification challenge being based on the identified variations between the observed behavioral characteristics and the behavior profile.

11. A system for verifying a user of a computer system, comprising:

a monitoring component configured to observe behavioral characteristics of the user's interactions with the computer system during a current session of computer system usage, the behavioral characteristics being based on command invocation behavioral characteristics;

a comparison component configured to identify variations between the observed behavioral characteristics and a behavioral profile developed based on prior command invocation behavioral characteristics of the user; and

a verification component configured to implement a verification procedure for the user to complete to continue the current session, the verification procedure being based on the identified variations between the observed behavioral characteristics and the behavioral profile;

wherein identifying variations between the observed behavioral characteristics and the behavioral profile includes, calculating a measure of distance between the observed behavioral characteristics and the behavioral profile, and wherein implementing a verification procedure for the user to continue the current session includes, defining a verification procedure based on the calculated measure of distance which includes a verification challenge to the user, the verification challenge being based on the identified variations between the observed behavioral characteristics and the behavior profile.

12. The system of claim 11 , further comprising:

a profiling component configured to develop the behavioral profile by identifying typical command invocation behavioral characteristics of the user from historical computer system usage data.

13. The system of claim 11 , wherein verification component is configured to implement the verification procedure further based on a risk level of the current session.

14. The system of claim 11 , wherein command invocation behavioral characteristics are selected from a group consisting of:

an order of command invocations;

a set of selected command options;

an order of entered command options;

a grammatical structure of a command invocation;

a set of words selected for a command invocation;

a order of words of a command invocation;

use of a shortcut for a command invocation;

a chosen method for a command invocation; and

a user input device used for command invocation.

15. The system of claim 11 , wherein the profiling component is further configured to modify the behavioral profile based on the observed behavioral characteristics of the user's interactions with the computer system during the current session of computer system usage.

16. The system of claim 11 , wherein the verification component is further configured to determine if the user is verified based on completion of the verification procedure by the user,

and further comprising a behavioral profile adaptation component configured to modify the behavioral profile based on the identified variations between the observed behavioral characteristics and the behavioral profile, if it is determined the user is verified.

17. The system of claim 11 , wherein the verification component is configured to provide the verification challenge to the user, the verification challenge being based on the identified variations between the observed behavioral characteristics and the behavioral profile, and to permit the user to continue the current session based on the user's response to the verification challenge.